This invention relates in general to sealing shafts and the like and, more particularly, to a seal that is particularly adapted for use with an overhang that encircles it.
A type of antifriction bearing, known as an all-purpose bearing, exists which is furnished as a sealed self-contained assembly that is preset and prelubricated. As such, the bearing is simp1y fitted over an axle journal and into a housing to enable the axle to rotate relative to the housing or vice-versa. All-purpose bearings have experienced wide-spread use on axles of railway cars, but they are also used in other applications, such as for crane wheels, table rolls and shears, and even for the work rolls of rolling mills.
All-purpose bearings often operate in hostile environments, and this is particularly true when they are used at the journals of railway cars. Here they are subjected to contaminants, such as moisture and road grit, which must remain out of the interiors of the bearings to prevent premature failure. Hence, the presence of seals at the ends of all-purpose bearings.
The typical seal for an all-purpose bearing has a seal case which is fitted into an end of the outer race for the bearing and an elastomeric seal element which is bonded to the seal case and bears against a wear ring at the end of the corresponding inner race for the bearing. Actually, the seal element contacts the wear ring at two axially spaced locations, namely along a primary lip that is on the so-called oil side of the seal and also along dust or secondary lip that is on the air side. A garter spring encircles the primary lip to urge it snugly against the wear ring, where it is supported on a thin, yet continuous, film of lubricant known as an elastohydrodynamic oil film. The dust lip likewise bears against the wear ring, but merely under the bias of the elastomer from which the seal element is molded. Indeed, a separate seal and wear ring exists at each end of the typical all-purpose bearing.
In some installations where all-purpose bearings are used, the seals at the ends of those bearings are further protected by overhangs which project axially from backing members between which the bearing is clamped and encircle the wear rings. For example, on the typical journal for a rail car axle, the wear ring at the inboard end of the bearing bears against a cone backing ring that fits snugly against a shoulder at the inboard end of the journal, whereas the wear ring at the outboard end fits against an end cap that extends across the end face of the journal . Some backing rings and end caps have overhangs which project axially around the seals that encircle the wear ring against which they fit. The overhangs create a more tortuous route for contaminants to enter the bearing, and inasmuch as they rotate with the axle journal, they propel water and other contaminants away from the seals.
Whereas, the overhangs used with conventional all-purpose bearings are separate and apart from the seals which they protect, the seal of the present invention actually cooperates with the overhangs to establish additional barriers to the ingress of contaminants. Yet, the seal requires no special or additional procedures for assembling the bearing, nor does it impose any additional torque or drag during operation of the bearing.